The Environmental Protection Agency (EPA) sets guidelines for states to follow in designing and running vehicle inspection and maintenance (I/M) programs. The guidelines are designed to reduce pollutants in the air that are produced by vehicles having defective or improperly working emissions systems. The guidelines for automobile emissions testing programs set forth the minimum requirements to satisfy the Clean Air Act (CAA). One requirement is that the states periodically inspect vehicles that travel on the roadways. Included in the periodic inspection for newer vehicles is the checking of the vehicles on-board diagnostic system.
Vehicle emission inspection programs have traditionally analyzed vehicle exhaust under simulated driving conditions. One way to simulate driving conditions is to place the vehicle on rollers and run the vehicle at various speeds. Placing the vehicle on rollers and running the vehicle at selected speeds is undesirable because it is inconvenient, time consuming, and potentially dangerous.
Another method of performing a vehicle emissions inspection is to analyze the data stored on the on-board diagnostic system that was gathered during actual driving conditions. All vehicles manufactured since 1996 are required to have an on-board diagnostic system. The on-board diagnostic system includes one or more computer modules that are used to control various components, such as the engine and transmission. In addition, the on-board diagnostic systems monitor and store data indicative of emissions levels, such as, for example, data from oxygen sensors, the catalytic converter, the EGR valve, etc., that are obtained during actual driving conditions over a period of time and during key off conditions. The on-board diagnostic system sets a status flag to ensure that the vehicle has been driven under actual conditions for a sufficient period of time for the on-board diagnostic system to fully evaluate the emissions system. The status flag, or readiness code, is used to verify that error codes have not been cleared immediately prior to having the vehicle inspected.
A typical I/M program for 1996 and later models may include a manual examination of the emission system components and an electronic examination of the on-board diagnostic system. First, the inspector performs a visual check of the dashboard display, status indication, (or the malfunction indicator light “MIL”) and the selected emissions control components. Next, the inspector performs an inspection of the on-board diagnostic system. Typically, an “Off-Board Tool,” (OBT) such as a scan tool, code reader or similar hand-held instrument is used to extract data from the vehicle on-board diagnostic system in the form of Diagnostic Trouble Codes (DTCs), monitors, etc.
“Off-Board Tools,” (OBTs) such as, for example, scan tools, are testing devices that interface with vehicle diagnostic systems to access, display, and/or print vehicle diagnostic information. On-Board Diagnostics Version II Scan Tools are one commonly known type of scan tool and are governed by a number of standards, such as, for example, SAE J1978 Rev. April 2002 and SAE J1979 Rev. April 2002.
There are a number of problems with existing OBTs when used for emissions testing programs. In order to be On-Board Diagnostics Version-II compliant, existing OBTs must automatically determine the proper communications protocol to use to connect to the vehicle. OBTs cannot acquire the communications protocol from a user, or host computer and remain On-Board Diagnostics Version-II compliant. Determining the proper protocol and establishing the communications link following the SAE standards requires a significant amount of time. In the event that the communications link between the OBT and the on-board diagnostic system drops out, under the SAE standards, the OBT must re-establish the link using the same process that the OBT used to establish the link in the first place.
Moreover, dropping the communications link is not uncommon and is particularly problematic in some vehicles. In certain vehicles, such as, for example, various model years of HYUNDAI, VW, DODGE, and VOLVO vehicles, many scan tools experience communications drop-outs quite often. The user will be using a scan tool and be examining, for example, 28 different parameters, one minute and suddenly there is no response for all but, for example, three of the parameters. This often occurs when one or more controllers, such as, the engine controller, which is typically the main On-Board Diagnostics Version-II controller, has dropped out, leaving only a secondary controller, such as, a transmission controller, talking with the OBT. As a result, the OBT must begin the entire session over again, which can take half a minute or more.
As noted above, under SAE specifications, protocol determination is an automatic (hands off) determination of the communication protocol the vehicle uses to support the On-Board Diagnostics Version-II functions. Some vehicles have multiple modules and these modules often use different communication protocols. Only one of these protocols, however, is used to obtain all of the On-Board Diagnostics Version-II information for the vehicle. Therefore, the OBT must be able to determine which protocol is the correct one to use for On-Board Diagnostics Version-II purposes. Section 6.4.1 and 6.4.2 the SAE J1978 spell out a procedure for trying four (4) or more protocols and determining which one is the On-Board Diagnostics Version-II protocol supported by the vehicle related to the appropriate functions. Although the specification requires that only one protocol be allowed to be used in any one vehicle to access all the supported On-Board Diagnostics Version-II functions, it does not mean than the vehicle cannot support more that one protocol. It only means that one protocol can be used as the On-Board Diagnostics Version-II link. Occasionally following the SAE specifications for determining the proper protocol results in using the wrong protocol, i.e. one that does not provide the most relevant information (e.g., the most emissions information). Problem vehicles include, for example, ones that supports both ISO 9141-2 (ISO) and ISO 14230-4 (Keyword 2000). In this example, the engine control module uses ISO 14230-4 as its protocol and the transmission control module uses ISO 9141-2. The engine controller is the module that supports the On-Board Diagnostics Version-II functions for the vehicle. But the SAE suggested procedure directs that the OBT test for ISO 9141-2 first and if one receives a reply, then that is the protocol to use for the link. This causes the OBT to incorrectly choose the protocol being used by the transmission as the On-Board Diagnostics Version-II protocol for this type of vehicle rather than the protocol being used by the engine controller. Now that the OBT is using the wrong protocol, ISO 9141-2, it is only talking to the transmission controller. The engine controller (and all the emissions information it has to offer) is not found. This type of problem can happen in other protocol combinations as well. Thus, under this same procedure, an OBT might select a protocol that ends up with far less emissions data than another protocol.
In addition, some vehicles employ multiple modules that communicate using the same protocol. This type of system is subject to one or more of the modules to losing their active communication with an OBT. If the OBT does not realize that one or more of the modules has dropped the link, it will not be showing complete/correct data. For example, certain VW models that use an engine control module and a transmission control module present a problem. After determining the On-Board Diagnostics Version-TI protocol and initializing both modules for communications one or the other module occasionally stops communicating. This problem can be seen while requesting information on several functions, such as the “View Data” function (also known as the “Live Data” function). For example, a user might notice during one View Data session that two modules report the state of the “MIL” and might notice on a subsequent View Data session on the same vehicle that only one module reports the MIL's state. The MIL's state from the other modules is now unknown. What happened is that, unknown to the user, one of the controllers dropped the communications link, so it did not respond to the request for the state of the MIL. These problems can result in information being misreported.
In addition, existing OBTs waste significant amounts of time during diagnostic test modes. Modern vehicles support a number of diagnostic test modes, such as Modes 01-09. Mode 01 is used to Request Current Powertrain Diagnostic Data, Mode 02 is used to Request Powertrain Freeze Frame Data, Mode 03 is used to Request Emission-Related Powertrain Diagnostic Trouble Codes (DTCs), Mode 04 is used to Clear/Reset Emission-Related Diagnostic Information, Mode 05 is used to Request Oxygen Sensor Monitoring Test Results, Mode 06 is used to Request on-Board Monitoring Test Results for Non-Continuously Monitored Systems, Mode 07 is used to Request On-Board Monitoring Test results for Continuously Monitored Systems, Mode 08 is used to Request Control of On-Board System, Tests, or Component, and Mode 09 is used to Request Vehicle Information.
Under the recommended practices developed by SAE, an OBT should wait for a response from the previous request, or “no response” timeout before sending another request. Significant amounts of time are wasted during test modes, such as, for example, a Mode 9 request, while the OBT waits to see if the on-board vehicle diagnostic system is going to send additional messages after the on-board vehicle diagnostic system has already sent all of its messages. Each communications protocol, such as, for example, J1850 PWM, J1850 VPW, ISO 9141-2, ISO 14230-4 and ISO 15765-4 has a different time out requirement and thus, the length of time or the “no response” timeout varies based on the communications protocol being used. Time out requirements are the length of time that a computer module has to respond to a request by the OBT.
Although, an OBT can initiate a request to the vehicle diagnostic system that should identify the number of computer modules that support the request, and the number of messages that each computer module will provide, the response is often incomplete or inaccurate. Often times, for example, a computer module will indicate that it has a certain number of messages, but will respond to a request with more than the indicated number of messages. Problems arise, for example, if an OBT is expecting two messages, one from a first computer module, and one from a second computer module, and the OBT stops waiting for responses after it receives two messages, even though both of the messages were actually from the second computer module. Thus, the OBT never receives the response from the first computer module.